Rotary hammer

ABSTRACT

A rotary hammer includes a spindle  18  which can be rotatably driven by an intermediate shaft  24  by way of a drive device. A tool holder  16  is arranged for rotation with the spindle  18,  and for releasably holding a bit or tool for selective rotation and/or reciprocation. A pneumatic hammering arrangement facilitates repeated impacting of the bit or tool for reciprocation within the tool holder ( 16 ). A mode change mechanism includes a knob  18  for selectively operating the rotary hammer in any of three modes, identified as a rotary drive only mode, a hammer only mode and a rotary hammer mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Reissue of U.S. Pat. No. 6,666,284 B2, issued Dec.23, 2003, which claims priority to Great Britain application Serial No.0008465, filed Apr. 17, 2000.

BACKGROUND OF THE INVENTION

This invention relates to a rotary hammer, and particularly relates to arotary hammer with a mode change mechanism for switching the rotaryhammer for operation in any one of a hammer only mode, a rotary driveonly mode and a rotary hammering mode.

In a hammer only mode of a conventional rotary hammer, a bit is insertedinto a tool holder of the hammer and is repeatedly struck by a hammeringmechanism and is not rotatably driven. In a rotary drive only mode, thebit is rotatably driven and is not subject to impacts from the hammeringmechanism. In a rotary hammering mode, the bit is repeatedly struck bythe hammering mechanism and is simultaneously rotatably driven.

Conventional rotary hammers of this type typically include a spindlemounted for rotation within a housing of the hammer which can be drivenby a rotary drive arrangement, selectively engageable and disengageablewith a pinion driven by a motor of the hammer. The spindle rotatablydrives a tool holder of the hammer which in turn rotatably drives a toolor bit releasably secured within the hammer. A piston is generallyslideably located within the spindle and is reciprocally driven by ahammer drive mechanism which translates the rotary drive of a hammermotor to a reciprocating drive of the piston. A ram, also slideablylocated within the spindle, forward of the piston, follows thereciprocation of the piston due to successive reversing pressures in anair cushion within the spindle between the piston and the ram. The ramrepeatedly impacts an anvil slideably located within the spindle forwardof the ram which transfers the forward impacts from the ram to the toolor bit, for limited reciprocation within the tool holder at the front ofthe hammer. The mode change mechanisms for such hammers can selectivelyengage and disengage the rotary drive to the spindle and thereciprocating drive to the piston.

In a known type of mode change mechanism, a single mode change actuatoris used to switch the hammer between different modes. However,mechanisms of this type tend to be relatively complex, use parts whichare intricate and/or difficult to manufacture inexpensively in bulk,with sturdy qualities that can withstand sustained use of the hammer,and/or are relatively difficult to assemble.

A known mode change arrangement is disclosed in U.S. Pat. No. 5,159,986,and includes a mode change knob having a first cam element foractivating and de-activating hammering, and a second cam for activatingand deactivating rotary drive. The disclosed arrangement also includesthe option of operating at either of two drive speeds. In a firstposition of the first cam element, rearward movement of the spindle isblocked, which prevents the drive from being transmitted to the hammerdrive arrangement. In a second position of the first cam, rearwardmovement of the spindle occurs when the tool or bit is pressed against awork surface. This rearward movement of the spindle results in theengagement of two coupling parts which allows the drive to betransmitted from an intermediate shaft to the hammer drive arrangement.

The second cam arrangement, as described in U.S. Pat. No. 5,159,986, isused to guide an adjustment element along a rod mounted in the housingof the hammer, which adjustment element engages spindle drive gears toshift the gears between three positions. In a first of the threepositions, a drive gear engages a spindle lock to prevent rotation ofthe spindle, and relates to of a surface of the first cam whereby driveis transmitted to the hammer drive arrangement. In a second position, afirst drive gear engages the intermediate shaft to drive the spindle ata first speed of rotation, and, in a third position, a second drive gearengages the intermediate shaft to drive the spindle at a second speed.The three positions of the drive gears, as they relate to theorientation of the second cam element, are co-ordinated with theblocking and non-blocking positions, in relation to the orientation ofthe first cam element, in order to co-ordinate the activation of thespindle at the required speed with the activation of hammering.

The mode change arrangement as disclosed in U.S. Pat. No. 5,159,986requires many non-standard type parts such as the first and second camsurfaces, an adjustment element, a bearing and a cage, which have tointeract to change between the modes of operation. Such parts arerelatively expensive to manufacture in such a way that the parts cansurvive sustained use of the hammer and still provide smooth changesbetween the different modes of operation of the hammer. Also, theassembling of the parts to provide such a mode change arrangement isrelatively difficult, which further adds to the cost of manufacturingsuch hammers. Further, a biasing means between the knob and theadjustment element is required to bias the gears or teeth into positionfor meshing until one of the gears has rotated sufficiently to allowactual meshing to occur. This results in additional cost and complexity.

SUMMARY OF THE INVENTION

Therefore, it is an object of this invention to provide a rotary hammerhaving a simple and reliable mode change mechanism for selectivelyoperating in a hammer only mode, a rotary hammer mode, or a rotary driveonly mode.

Another object of this invention is to provide a rotary hammer having amode change mechanism which utilizes primarily standard engineeringparts such as splined shafts, gear wheels, splined sleeves and springs.

A further object of this invention is to provide a rotary hammer havinga mode change mechanism which utilizes primarily standard engineeringparts which are sturdy and inexpensive to manufacture, and relativelyeasy to assemble.

With these and other objects in mind, this invention contemplates arotary hammer, which includes an intermediate shaft rotatably drivableby a motor, and a spindle which can be driven about an axis thereof bythe intermediate shaft through a spindle drive arrangement. The rotaryhammer further includes a tool holder arranged for rotation with thespindle for releasibly holding a bit or a tool for reciprocation, apneumatic hammering arrangement located within the spindle which canrepeatedly impact the bit or tool held within the tool holder. Thepneumatic hammering arrangement includes a piston which can bereciprocally driven by a hammer drive arrangement for translating rotarydrive from the intermediate shaft to a reciprocating drive for thepiston. The rotary hammer further includes a mode changing mechanism forchanging the operation of the hammer amongst a hammer only mode, arotary hammer mode, and a rotary drive only mode. The mode changemechanism includes a spindle driving member rotatably mounted on theintermediate shaft for driving the spindle drive arrangement, a hammerdriving sleeve rotatably mounted on the intermediate shaft for drivingthe hammer drive arrangement, and a mode change sleeve, which surroundsthe intermediate shaft and which is permanently driven by and shiftablealong the intermediate shaft. The switching of the actuator by a usershifts the mode change sleeve along the intermediate shaft to any one ofthree positions, such that, in a first rotary drive only position, themode change sleeve transmits rotary drive to the spindle driving memberand to transmit rotary drive to the spindle drive arrangement. In asecond hammer only position, the mode change sleeve transmits rotarydrive to the hammer driving sleeve to transmit rotary drive to thehammer drive arrangement. In a third rotary hammer position, the modechange sleeve transmits rotary drive to the spindle driving member andto the hammer driving sleeve to transmit rotary drive to the spindledrive arrangement and to the hammer drive arrangement.

This invention further contemplates the mounting of the hammer drivesleeve and the spindle drive member rotatably on the intermediate shaft,and the mounting of the mode change sleeve shiftably and non-rotatablyalong the intermediate shaft. This facilitates use of the mode changesleeve to transfer rotary drive from the intermediate shaft to thehammer drive sleeve and/or the spindle drive member by simply shiftingthe mode change sleeve along the intermediate shaft to selectivelyengage the hammer drive sleeve and/or the spindle drive member. Theparts required for this mode change mechanism are standard engineeringparts, such as a shaft and sleeves rotatable or non-rotatable on theshaft and optionally shiftable along the shaft. The sleeves have partssuch as gear wheels or teeth, which are selectively engageable with eachother. Such parts can be manufactured inexpensively and of sturdystructure, and can be easily assembled to provide a simple and reliablemode change mechanism.

In further contemplation of this invention, preferably, an intermediateshaft driving member, preferably a gear which is non-rotatable on theintermediate shaft, is in permanent engagement with a mode change sleevedriven member, preferably a set of teeth on the mode change sleeve, sothat rotation of the intermediate shaft rotatingly drives the modechange sleeve.

Still, in further contemplation of this invention, in a preferredarrangement, the hammer drive sleeve is located towards the rear of themode change sleeve and has a driven member, preferably a set of teeth,which is engageable with a driving member, also preferably a set ofteeth, on the mode change sleeve to transmit rotary drive from theintermediate shaft to the hammer drive sleeve. Preferably, the modechange sleeve driven member, which engages the intermediate shaftdriving member, is axially extended and also forms the mode changesleeve driving member, which is engageable with the hammer drive sleevedriven member, to transmit rotary drive from the intermediate shaft tothe hammer drive arrangement. Using a single extended driven and drivingmember, such as an extended set of teeth, again simplifies the structureof the mode change sleeve.

This invention also contemplates, in a preferred arrangement, thespindle drive member being located towards the front of the mode changesleeve and has a driven member, preferably a set of teeth, on the modechange sleeve to transmit rotary drive from the intermediate shaft tothe spindle drive member. Again, it is preferred that the mode changesleeve driven member which engages the intermediate shaft driving memberis axially extended to also form the mode change sleeve driving memberwhich is engageable with the spindle drive member to transfer rotarydrive from the intermediate shaft to the spindle drive member. Using asingle extended driven and driving member, such as an extended set ofteeth, again simplifies the structure of the mode change sleeve.

The spindle drive member may be a spindle drive sleeve which isrotatably mounted on the outside of the intermediate shaft.Alternatively, the spindle drive member may be a spindle drive pinionwhich is rotatably mounted within the front end of the intermediateshaft.

When the above preferred arrangements are both used on the hammer, themode change mechanism is arranged such that, in a first rotary driveonly position, the mode change sleeve is shifted to a forward positionon the intermediate shaft to transmit rotary drive to the spindledriving member by way of the mode change sleeve driving member and thespindle drive member driven member. In a second hammer only position,the mode change sleeve is shifted to a rearward position on theintermediate shaft to transmit rotary drive to the hammer driving sleeveby way of the mode change sleeve driving member and the hammer drivesleeve driven member. In a third rotary hammer position, the mode changesleeve is shifted to an intermediate position on the intermediate shaftbetween the forward and rearward positions and transmits rotary drive tothe spindle driving member and transmits rotary drive to the hammerdriving sleeve.

In a preferred embodiment, the switching of the single actuator shiftsthe mode change sleeve by way of a mode change member. The mode changemember may be mounted on a housing part of the hammer so as to beslideable in a direction substantially parallel to the intermediateshaft. The mode change member is preferably provided with a mode changearm, preferably a ring, which extends laterally of the mode changemember. The mode change arm at least partly surrounds at least a part ofthe mode change sleeve and is connected to the mode change sleeve suchthat shifting of the mode change member shifts the mode change sleeve byway of the mode change arm amongst the three positions.

In order to insure transmission of rotary drive between the parts, whichmay not initially be in meshing alignment when the hammer is firstswitched to one of the three modes of operation, a biasing arrangementis located between the actuator and the mode change sleeve in order tobias the sleeve towards a position on the intermediate shaft whichcorresponds to the position to which the actuator is switched. When thehammer includes a mode change member having a mode change arm asdescribed above, it is preferred that the biasing arrangement includes afirst spring means located between a forward end of the mode changesleeve and a forward facing part of the mode change arm and a secondspring means located between a rearward end of the mode change sleeveand a rearward facing part of the mode change arm.

Preferably, a spindle lock is provided on the hammer to lock the spindleagainst rotation when the hammer is in the hammer only mode. When thehammer includes a mode change member, as described above, it ispreferred that the spindle lock include a first locking means located onthe mode change member, which first locking means is engageable with asecond locking means provided on the spindle when the mode change memberis shifted to a hammer only mode position to lock the spindle againstrotation.

The actuator may be a rotatable knob mounted on a housing part of thehammer such that the rotation of the knob rotates an eccentric pin whichpin is slideably engaged, preferably with a slot in the mode changemember, in order to shift the mode change member and thereby shift themode change sleeve amongst the three mode positions.

The mode change mechanism described above is suited to the type ofhammer having a pneumatic hammering arrangement which includes areciprocally driven piston, which reciprocally drives a ram by way of aclosed air cushion. The ram repeatedly impacts an anvil which is driven,in a forward direction, to impact a bit or tool held in the tool holder.This arrangement is particularly suited to the type of hammer in whichthe intermediate shaft is substantially parallel to the spindle.

It is preferred that the spindle drive member include a driving member,preferably a gear, which is in permanent engagement with the spindledrive engagement, which preferably includes a gear.

It is also preferred that the hammer drive arrangement is a wobble platedrive arrangement.

Preferably, a releasable detent arrangement is provided for releasablylatching the actuator in the required mode switch position. This isimportant if the hammer includes means for biasing the mode changemechanism into meshing engagement when the meshing parts are initiallynot aligned.

Other objects, features and advantages of the present invention willbecome more fully apparent from the following detailed description ofthe preferred embodiment, the appended claims and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is an exploded perspective view showing a layout of thecomponents of a rotary hammer mode change mechanism in accordance withcertain principles of the invention;

FIG. 2a is a sectional view showing a first embodiment of a rotaryhammer, including the mode change mechanism of FIG. 1, in a rotary driveonly mode, or drilling mode, in accordance with certain principles ofthe invention;

FIG. 2b is a sectional view showing the rotary hammer of FIG. 2a,including the mode change mechanism of FIG. 1, in a rotary hammer modein accordance with certain principles of the invention;

FIG. 2c is a sectional view showing the rotary hammer of FIG. 2a,including the mode change mechanism of FIG. 1, in a hammer only mode inaccordance with certain principles of the invention;

FIG. 3 is a sectional view showing a second embodiment of a rotaryhammer, including the mode change mechanism of FIG. 1, in a hammer onlymode in accordance with certain principles of the invention;

FIG. 4a is a sectional view showing the rotary hammer of FIG. 3,including the mode change mechanism of FIG. 1, in a rotary hammer modein accordance with certain principles of the invention; and

FIG. 4b is a sectional view showing the rotary hammer of FIG. 3,including the mode change mechanism of FIG. 1, in a rotary drive onlymode, or a drilling only mode, in accordance with certain principles ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring to FIGS. 1, 2a, 2b and 2c, a first embodiment of a rotaryhammer includes a forward housing part 2 and a central housing part 4,which are held together by threaded fasteners (not shown) to form ahousing for a hammer spindle, a spindle drive arrangement, a hammerdrive arrangement and a mode change mechanism. A resilient housing seal6 fits between the housing parts 2 and 4 in a complementary recessprovided in co-operating end surfaces of the housing parts to form aseal between the housing parts. The housing parts 2 and 4 are eachformed with semi-circular recesses 2a and 4a, respectively, whichco-operate to form a circular recess, lined with a ring section 6a ofthe housing seal 6, within which a mode change knob 8 is mounted forrotation about a mode change axis 12. The mode change knob 8 has an axlewith an enlarged portion 10 which is captured within the hammer housingwhen the housing parts 2 and 4 are assembled together. In this manner,the mode change knob 8 is secured to the hammer housing. An eccentricpin 14 is formed with and extends from an end of the mode change axlefor slideably moving a mode change member 68, as described below.

The rotary hammer includes a spindle 18 which is mounted for rotationwithin the hammer housing in a conventional manner. Also, a hollowpiston 20 is located slideably within the rear of the spindle 18 in aconventional manner. The hollow piston 20 is reciprocated within thespindle 18 by a hammer drive arrangement as described in more detailbelow. A ram 21 follows the reciprocation of the piston 20 in the usualmanner due to successive reversing pressures in an air cushion withinthe spindle 18 between the piston and the ram. The reciprocation of theram 21 causes the ram to repeatedly impact an anvil 22 which repeatedlyimpacts a tool or bit (not shown). The tool or bit is releasably securedto the rotary hammer by a tool holder of conventional design, such asand SDS-Plus type tool holder 16, which enables the tool or bit toreciprocate within the tool holder to transfer the forward impact of theanvil 22 to a surface to be worked, such as a concrete block. The toolholder 16 also transmits rotary drive from the spindle 18 to the tool orbit secured within the tool holder.

The rotary hammer is driven by a motor (not shown), which has a pinion(not shown) for rotatably driving an intermediate shaft 24 by way of adrive gear 32. The intermediate shaft 24 is mounted for rotation withinthe hammer housing, parallel to the hammer spindle 18 by means of arearward bearing 26 and a forward bearing 28. A spring washer 30 urgesthe intermediate shaft 24 rearwardly and is used to damp anyreciprocatory motion which is transmitted to the intermediate shaft byway of a wobble plate hammer drive arrangement described below. Theintermediate shaft 24 has a driving gear 50, either integrally formedtherewith or press fit onto shaft so that the driving gear rotates withthe shaft. Thus, whenever power is supplied to the motor, the drivinggear 50 rotates along with the intermediate shaft 24.

The hammer drive arrangement includes a hammer drive sleeve 34 which isrotatably mounted on the intermediate 24 and which has a wobble platetrack 36 formed around the sleeve at an angle to the axis of theintermediate shaft. A wobble plate ring 38, having an extending pin 40,is mounted for rotation around the wobble plate track 36 by way of ballbearings 39 in a conventional manner. The end of the wobble pin 40,remote from the wobble plate ring 38, is mounted through an aperture ina trunnion 42 which is pivotally mounted to the rear end of the hollowpiston 20 by way of two arms 44 having aligned apertures formedtherethrough. Thus, when the hammer drive sleeve 34 is rotatably driveabout the intermediate shaft 24, a wobble plate drive (which is formedby the wobble plate track 36, the wobble plate ring 38, the ballbearings 39, the wobble pin 40, the trunnion 42 and the arms 44)reciprocally drives the hollow piston 20 in a conventional manner. Thehammer drive sleeve 34 has a set of driven splines 48 formed on aforward end of the sleeve. The driven splines 48 are selectivelyengageable with the driving gear 50 by way of the mode change mechanismdescribed below. When the intermediate shaft 24 is rotatably driven bythe motor pinion, and the mode change mechanism engages the drivingsplines 48 of the hammer drive sleeve 34, (1) the driving gear 50rotatably drives the hammer drive sleeve, (2) the piston 20 isreciprocally driven by the wobble plate drive, and (3) the tool or bitmounted in the tool holder 16 is repeatedly impacted by the anvil 22 byway of the action of the ram 21.

The spindle drive member includes a spindle drive sleeve 56 which ismounted for rotation about the intermediate shaft 24. The spindle sleeve56 includes a set of driving teeth 60 at the forward end thereof whichare permanently in engagement with the teeth of a spindle drive gear 62.The spindle drive gear 62 is mounted non-rotatably on the spindle 18 byway of a driving gear 64 which has a set of teeth formed on the internalcircumferential surface thereof which are permanently engaged with a setof drive teeth 66 formed on the outer cylindrical surface of the spindle18. Thus, when the spindle drive sleeve 56 is rotatably driven, thespindle 18 is rotatably driven, and this rotary drive is transferred tothe tool or bit by way of the tool holder 16. The drive sleeve 56 has adriven gear 58 located at a rearward end of the drive sleeve which canbe selectively driven by the intermediate shaft driving gear 50 by wayof the mode change mechanism.

The mode change mechanism, which can be used to selectively actuate thehammer drive arrangement and/or the spindle drive arrangement, includesthe mode change member 68 which is slideably mounted within the housingon guide members (not shown) mounted within or formed integrally withthe housing. The mode change member 68 is formed with a set of spindlelock teeth 70 which can be selectively engaged with the spindle drivegear 62 to lock the spindle, against rotation, by way of the drive gear.The mode change membr 68 has a mode change ring 72 secured to a centralregion thereof so that the ring extends laterally of the member. Themode change ring 72 is slideably mounted over a mode change sleeve 52. Apair of coil springs, forward spring 76 and rearward spring 78, aremounted surrounding the mode change sleeve 52 in order to position themode change ring 72 with respect to the mode change sleeve. The forwardspring 76 acts between an annular flange 84, located towards the forwardend of the mode change sleeve 52, and the forward annular face of themode change ring 72. The rearward spring 78 acts between the rearwardannular face of the mode change ring 72 and a stop ring 80, which ismounted towards the rearward end of the mode change sleeve 52 by a snapring 82.

The mode change member 68 is formed with a slot 74 which extends in adirection substantially perpendicular to the direction of sliding of themode change member. The eccentric pin 14 of the mode change knob 8 isslideably received within the slot 74 in the mode change member 68. Inthis manner, as the mode change knob 8 is rotated by the user of thehammer about the axis of the knob, the eccentric pin slides along theslot 74. This causes the mode change member 68 to slide forwards orbackwards within the housing in order to move the mode changing ring 72forwards or backwards with respect to the intermediate shaft 24 and tomove the spindle lock teeth 70 forwards or backwards with respect to thespindle drive gear 62.

A detent arrangement includes a spring 90 and a ball bearing 92 and issituated in a bore 94 provided in the housing part 4 so that the ballbearing is urged by the spring into one of a number of pockets (notshown) which are provided in the underside of the knob 8. Each pocket ispositioned so that it corresponds to a mode position of the knob 8, withthe ball bearing 92 resting in a first-elected one of the pockets whichis associated with the most recently selected mode of operation. Whenthe knob 8 is moved toward one of the other mode positions in order tochange the operating mode of the rotary hammer to a newly selected modeposition, a user must overcome the biasing force of the spring 90 topush the ball bearing 92 out of the first-elected one of the pockets inthe underside of the knob. Once the knob 8 is moved into the newlyselected mode position, the ball bearing 92 is urged by the spring 90 toengage a second-selected one of the pockets which corresponds to thenewly selected mode position. Once the ball seats in the second-selectedone of the pockets, the knob 8 is latched against movement out of thenewly selected mode position.

As shown in FIG. 2a, the rotary hammer is in the rotary drive only modein which the spindle 18 is driven rotationally and the hammer drivearrangement is disengaged. The mode change knob 8 is in the farthestposition to which it can be rotated in a clockwise direction and so theeccentric pin 14 lies forwardly of the axis 12 of the knob and maintainsthe mode change member 68 in the forwardmost position. In this position,the spindle lock teeth 70 are located forward of the spindle drive gear62 which is free to rotate in order to rotationally drive the spindle18. The mode changing ring 72 is in its forwardmost position and urgesthe mode change sleeve 52 forwardly by way of the spring 76. In thismanner, the internal teeth 54 of the sleeve 52 are disengaged from thehammer drive splines 48 on the hammer drive sleeve 34 and so that theinternal teeth 54 of the mode change sleeve 52 are engaged with thedriving gear 50 on the intermediate shaft 24 and the driven gear 58 onthe spindle drive sleeve 56.

As the internal teeth 54 are disengaged from the hammer drive splines48, rotation of the intermediate shaft 24 is not transmitted to thehammer drive sleeve 34 which remains stationary as the intermediateshaft is rotated by the motor. Thus, no hammering action occurs.However, the engagement of the internal teeth 54 of the mode changesleeve 52 with the driving gear 50 of the intermediate shaft 24 and thedriven gear 58 of the spindle drive sleeve 56 transmits rotary drivefrom the intermediate shaft to the spindle drive sleeve. This rotarydrive is then transmitted to the spindle 18 by way of the driving teeth60 on the spindle drive sleeve 56, the spindle drive gear 62 and thespindle drive ring 64. Accordingly, the rotary hammer operates in therotary drive only or drilling mode.

The rotary hammer is moved into rotary drive only mode by rotating themode change knob 8 clockwise, and the knob is latched in its rotarydrive only position by the detent arrangement 90 and 92. When the rotaryhammer is moved into the rotary drive only mode from the hammer onlymode as the knob 8 is rotated clockwise, it is possible that theinternal teeth 54 of the mode change sleeve 52 are not in alignment withthe teeth 60 of the drive gear 58 of the spindle drive sleeve 56. Ifthis is so, then as the mode change ring 72 is shifted forwardly and theforward movement of the mode change sleeve 52 is blocked by themis-aligned teeth, the spring 76 is compressed and acts to urge the modechange sleeve toward its forward position. Thus, with the knob 8 latchedin the rotary drive only position, as soon as the intermediate shaft 24has rotated by a small angle required to align the internal teeth 54with the teeth of the driven gear 58, the spring 76 urges the modechange sleeve 52 forwardly into the position shown in FIG. 2a so thatthe internal teeth 54 of the mode change sleeve 52 mesh with the drivegear 58 of the spindle drive gear 56. Thereafter, rotation of theintermediate shaft 24 is transmitted to the spindle 18.

As shown in FIG. 2b, the rotary hammer is in the rotary hammer mode inwhich the spindle 18 is driven rotationally and the hammer drive isengaged. The mode change knob 8 is in an intermediate position and theeccentric pin 14 is located above the axis 12 of the mode change knoband maintains the mode change member 68 in an intermediate position. Inthis position, the spindle lock teeth 70 remain located forward of thespindle drive gear 62, which is free to rotate in order to rotationallydrive the spindle 18. The mode change ring 72 is in an intermediateposition and urges the mode change sleeve 52 into an intermediaryposition by way of the spring 76 or the spring 78, depending on theprevious mode of operation of the rotary hammer. In this intermediateposition, the internal teeth 54 of the sleeve 52 are engaged with thehammer driven splines 48 on the hammer drive sleeve 34 and with thedriving gear 58 on the spindle drive sleeve 56.

As the internal teeth 54 are engaged with the hammer driven splines 48,rotation of the intermediate shaft 24 is transmitted to the hammer drivesleeve 34 which rotates with the intermediate shaft. Thus, rotary drivefrom the motor is translated into a reciprocating drive of the hollowpiston 20 by way of the driving gear 50 of the intermediate shaft, themode change sleeve 52, the hammer driven splines 48 on the hammer drivesleeve 34 and the wobble plate mechanism, whereby hammering actionoccurs. The engagement of the internal teeth 54 of the mode changesleeve 52 with the driving gear 50 of the intermediate shaft 24 and thedriven gear 58 of the spline drive sleeve 56 transmits rotary drive fromthe intermediate shaft to the spindle drive sleeve 52. This rotary driveis then transmitted to the spindle 18 by way of the driving teeth 60 onthe spindle drive sleeve 56, the spindle drive gear 62 and the spindledrive ring 64. Accordingly, the rotary hammer operates in the rotaryhammer mode. Note that the rotary hammer can be moved into the rotaryhammer mode by rotating the mode change knob 8 either counter-clockwisefrom the rotary drive only position or clockwise from the hammer onlymode position.

When the rotary hammer is moved into the rotary hammer mode from therotary drive only mode as the knob 8 is rotated in a counter-clockwisedirection, it is possible that the internal teeth 54 of the mode changesleeve 52 are not in alignment with the driven splines 48 of the hammerdrive sleeve 34. In this instance, as the mode change ring 72 is shiftedrearwardly and the rearward movement of the mode change sleeve 52 isblocked by the mis-aligned teeth, the spring 78 is compressed and actsto urge the mode change sleeve 52 towards the its intermediate position.Thus, with the knob 8 latched in the rotary hammer position, as soon asthe intermediate shaft 24 has rotated by the small angle required toalign the splines 48 of the hammer driving sleeve 34 with the internalteeth 54 of the mode change sleeve 52, the spring 78 urges the modechange sleeve rearwardly into the position shown in FIG. 2b so that theinternal teeth 54 mesh with the splines 48. Thereafter, rotation of theintermediate shaft 24 is transmitted to the hammer drive arrangement aswell as to the spindle drive arrangement.

When the rotary hammer is moved to the rotary hammer mode from thehammer only mode as the knob 8 is rotated clockwise, it is possible thatthe internal teeth 54 of the mode change sleeve 52 are not in alignmentwith the teeth of the driven gear 58 of the spindle drive sleeve 56. Ifthis is so, as the mode change ring 72 is shifted forwardly and theforward movement of the mode change sleeve 52 is blocked by themis-aligned teeth, the spring 76 is compressed and acts to urge the modechange sleeve 52 towards its intermediate position.

Thus, with the knob 8 latched in the rotary hammer position, as soon asthe intermediate shaft 24 has rotated by the small angle required toalign the teeth of the spindle drive sleeve 58 with the internal drivingteeth 54 of the mode change sleeve 52, the spring 76 urges mode changesleeve forwardly into the position shown in FIG. 2b so that the internalteeth 54 of the mode change sleeve meshes with the teeth of the spindledrive gear 58. Thereafter, rotation of the intermediate shaft 24 istransmitted to the spindle drive arrangement as well as to the hammerdrive arrangement.

As shown in FIG. 2c, the rotary hammer is in the hammer only mode inwhich the spindle 18 is locked against rotation and the hammer drivearrangement is engaged. The mode change knob 8 is latched in thefarthest position to which it can be rotated in a counter-clockwisedirection where the eccentric pin 14 is rearwardly of the axis 12 of themode change knob and maintains the mode change member 68 in its rearwardmost position. In this position, the spindle lock teeth 70 are inengagement with the spindle drive gear 62, where the spindle drive gearand the spindle 18 are locked against rotation.

In the hammer only mode, the mode change ring 72 is in its rearmostposition and urges the mode change sleeve 52 rearwardly by the way ofthe spring 78 so that the internal teeth 54 of the drive sleeve 52 areengaged with the hammer drive splines 48 on the hammer drive sleeve 34,whereby the internal teeth 54 are disengaged from the driven gear 58 onthe spindle drive sleeve 56. As the internal teeth 54 engage with thehammer drive splines 48, rotation of the intermediate shaft 24 istransmitted to the hammer drive sleeve 34, which rotates theintermediate shaft. This rotational drive to the hammer drive sleeve 34is translated into reciprocating drive for the piston 20 by way of thehammer drive arrangement. Thus, hammering action occurs. Thedisengagement of the internal teeth 54 of the mode change sleeve 52 fromthe driven gear 58 of the spindle drive sleeve 56 facilitates that norotary drive is transmitted from the intermediate shaft 24 to thespindle drive sleeve which, therefore, remains stationary as theintermediate shaft rotates. Accordingly, the rotary hammer operates inthe hammer only mode.

The rotary hammer is moved into the hammer only mode by rotating themode change knob 8 counter-clockwise. When the rotary hammer is movedinto the hammer only mode from the rotary drive only mode as the knob 8is rotated counter-clockwise, it is possible that the internal teeth 54of the mode change sleeve 52 are not in alignment with the drivensplines 48 on the hammer drive sleeve 34. If this is the case, then asthe mode change ring 72 is shifted rearwardly and the rearward movementof the mode change sleeve 52 is blocked by the mis-aligned teeth, thespring 78 is compressed and acts to urge the mode change sleeve towardsits rearmost position. Thus, with the knob 8 latched in the hammer onlyposition, as soon as the intermediate shaft 24 has rotated by the smallangle required to align the internal teeth 54 with the driven splines 48of the hammer drive sleeve 34, the spring 78 urges the mode changesleeve 52 rearwardly into the position shown in FIG. 2c, so that theinternal teeth 54 mesh with the driven splines. Thereafter, rotation ofthe intermediate shaft 24 is transmitted to the hammer drive sleeve 34.

A second embodiment of a rotary hammer having a mode change mechanismaccording to the present invention is shown in FIGS. 3, 4a and 4b. Thesecond embodiment is similar to the first embodiment of the rotaryhammer, with like parts identified by like numerals, the differencebeing that the spindle drive member is a spindle drive pinion 56′. Asshown in FIGS. 3, 4a and 4b, the front end of a motor drives theintermediate shaft 24 of the rotary hammer by way of a motor pinion 23and the drive gear 32 of the intermediate shaft. In this way, theintermediate shaft 24 is always driven in rotation when the motor isswitched on. The spindle drive pinion 56′ has a rearward axialprojection 70 which is rotatably mounted within a co-operating recess 72within the front part of the intermediate shaft 24 by way of a needlebearing 74. Thus, the spindle drive pinion 56′ can rotate relative tothe intermediate shaft 24. The forward end of the spindle drive pinion56′ is rotatably mounted in a bearing 28 mounted in the rotary hammerhousing. In the same way described above, rotary drive is transmittedfrom the intermediate shaft 24 to the spindle drive pinion 56′ by themode change sleeve 52 to rotatably drive the spindle 18 by way of thespindle drive gear 62.

The hammer drive sleeve 34 is rotatably mounted on the intermediateshaft 24 by way of needle bearings 76 and 78. Again, the hammer drivesleeve 34 can be selectively rotationally driven by the intermediateshaft 24 by way of the mode change sleeve 52 to initiate the hammeringoperation. The mode change sleeve 52 is axially switchable by anactuator linkage, similar to the type described above, between threepositions to hammer only mode (FIG. 3), rotary hammer mode (FIG. 4a) androtary drive only or drill only mode (FIG. 4b), in the manner describedabove.

The hammer drive sleeve 34 and intermediate shaft are supported by anintermediate support bearing arrangement 129. The hammer drive sleeve 34has formed on its external surface, forwardly of the wobble bearingarrangement 36, 38, 39, an annular channel 140 within which runs a setof bearing balls 142. The bearing balls 142 run between an inner raceformed within the annular channel 140 of the hammer drive sleeve 34 andan outer race 144 formed in a bearing ring 146. The bearing ring 146 isused to support the intermediate shaft 24 and hammer drive sleeve 34within the housing 2, 4. Thus, the intermediate shaft 24 is supported inthe housing parts 2 and 4 by the rearward bearing 26, the forwardbearing 28, and the intermediate support bearing arrangement 129 via thehammer drive sleeve 34.

While the embodiments described above refer to rotary hammers withinwhich the motor is in line with the hammer spindle (i.e., parallelthereto), the mode change mechanism is also suitable for the so calledL-shaped hammers in which the axis of the motor is perpendicular to thespindle. In such L-shaped rotary hammers, the motor pinion will extendinto the hammer housing from below and will mesh with an intermediateshaft drive gear (replacing the gear 32) which is a bevel gear.

In general, the above-identified embodiments are not to be construed aslimiting the breadth of the present invention. Modifications, and otheralternative constructions, will be apparent which are within the spiritand scope of the invention as defined in the appended claims.

1. A rotary hammer, which comprises: an intermediate shaft (24) which isrotatably driven by a motor of the rotary hammer when power is suppliedto the motor; a spindle (18) which can be driven in rotation about itsaxis by the intermediate shaft 24 through a spindle drive arrangement(62,64); a tool holder (16) arranged for rotation with the spindle (18)for releasably holding a bit or a tool such that the bit or tool canreciprocate; a pneumatic hammering arrangement (20,21,22) located withinthe spindle (18) which can repeatedly impact the bit or tool held withinthe tool holder (16); said pneumatic hammering arrangement comprising apiston (20) which can be reciprocally driven by a hammer drivearrangement (34,36,38,39,40,42) which can translate rotary drive fromthe intermediate shaft (24) to a reciprocating drive to the piston (20);and a mode change mechanism for changing the operation of the rotaryhammer to operate in any of three modes, a rotary drive only mode, ahammer only mode or a rotary hammer mode; said mode change mechanismcomprising: a single actuator (8) switchable by a user of the rotaryhammer amongst the three modes of operation; a spindle driving member(56) rotatable on the intermediate shaft (24) for driving the spindledrive arrangement (62,64); a hammer driving sleeve (34) rotatable on theintermediate shaft (24) for driving the hammer drive arrangement(34,36,38,39,40,42); and a mode change sleeve (52) which is permanentlydriven by the intermediate shaft ( 24 ) and shiftable along theintermediate shaft (24) to change the operation of the rotary hammer tooperate in any of the three modes; where, upon the switching of theactuator (8) by a user, shifts the mode change sleeve (52) along theintermediate shaft (24) amongst the three modes positions, such that ina first rotary drive only position the mode change sleeve (52) transmitsrotary drive to the spindle driving member (56) to transmit rotary driveto the spindle drive arrangement (62,64), in a second hammer onlyposition the mode change sleeve (52) transmits rotary drive to thehammer driving sleeve (34) to transmit rotary drive to the hammer drivearrangement (34,36,38,39,40,42), and in a third rotary hammer positionthe mode change sleeve (52) transmits rotary drive to the spindledriving member (56) and to the hammer driving sleeve (34) to transmitrotary drive to the spindle drive arrangement (62,64) and to the hammerdrive arrangement (34,36,38,39,40,42).
 2. The rotary hammer according toclaim 1, which further comprises: a driven member (54) on the modechange sleeve (52); a driving member (50) mounted non-rotatably on theintermediate shaft (24) in permanent engagement with the driven member(54), so that rotation of the intermediate shaft rotatably drives themode change sleeve.
 3. The rotary hammer according to claim 1, whichfurther comprises: a driving member (54) on the mode change sleeve (52);a driven member (48) on the hammer drive sleeve (34); and wherein thehammer drive sleeve (34) is located towards the rear of the mode changesleeve (52) and the driven member (48) is engageable with the drivemember (54) to transmit rotary drive from the intermediate shaft (24) tothe hammer drive sleeve (34).
 4. The rotary hammer according to claim 3,wherein a driven member (54) on the mode change sleeve (52) whichengages a driving member (50) on the intermediate shaft (24) is axiallyextended to form the driving member (54) of the mode change sleeve (52)which is engageable with the driven member (48) on the hammer drivesleeve (34).
 5. The rotary hammer according to claim 1, which furthercomprises: a driven member (58) on the spindle drive member (56); adriving member (54) on the mode change sleeve (52); and wherein thespindle drive member (56) is located towards the front of the modechange sleeve (52) and the driven member (58) is engageable with thedriving member (54) to transmit rotary drive from the intermediate shaft(24) to the spindle drive member (56).
 6. The rotary hammer according toclaim 5, wherein a driven member (54) of the mode change sleeve (52)which engages a driving member (50) of the intermediate shaft (24) isaxially extended to form the driving member (54) which is engageablewith the driven member (58) on the spindle drive sleeve (56).
 7. Therotary hammer according to claim 1, which further comprises: a drivenmember (48) on the hammer drive sleeve (34); a driving member (54) onthe mode change sleeve (52); a driven member (58) on the spindle drivemember (56); the hammer drive sleeve (34) is located towards the rear ofthe mode change sleeve (52) and the driven member is engageable with thedriving member (54) to transmit rotary drive from the intermediate shaft(24) to the hammer drive sleeve (34); the spindle drive member (56) islocated towards the front of the mode change sleeve (52) and the drivenmember (58) is engageable with the driving member (54) to transmitrotary drive from the intermediate shaft (24) to the spindle drivemember (56); and the mode change mechanism is arranged such that in afirst rotary drive only position the mode change sleeve (52) is shiftedto a forward position on the intermediate shaft (24) to transmit rotarydrive to spindle driving member (56) through the driving member (54) andthe driven member 58, in a second hammer only position the mode changesleeve (52) is shifted to a rearward position on the intermediate shaft(24) to transmit rotary drive to the hammer driving sleeve (34) throughthe driving member (54) and the driven member (48), and in a thirdrotary hammer position the mode change sleeve (52) is shifted to anintermediate position on the intermediate shaft (24) between the forwardand rearward positions and transmits rotary drive to the spindle drivingmember (56) through the driving member (54) and the driven member (58)and transmits rotary drive to the hammer driving sleeve (34) through thedriving member (54) and the driven member (48).
 8. The rotary hammeraccording to claim 1, which further comprises: a mode changing member(68); and wherein the switching of the single actuator (8) shifts themode change sleeve (52) through the mode change member (68).
 9. Therotary hammer according to claim 8, which further comprises: a housingpart (2,4); and the mode change member (68) is mounted on the housingpart (2,4) of the rotary hammer so as to be slideable in a directionsubstantially parallel to the intermediate shaft (24).
 10. The rotaryhammer according to claim 8, which further comprises: a mode change arm(72) on the mode change member (68); and wherein the mode change arm(72) extends laterally of the mode change member (68) with the arm (72)surrounding at least a part of the mode change sleeve (52) and isconnected to the mode change sleeve (52) such that shifting of the modechange member (68) shifts the mode change sleeve (52) through the modechange arm (72) amongst the three mode positions.
 11. The rotary hammeraccording to claim 8, which further comprises: a housing part (2,4); arotatable knob (8) forms the actuator (8) and is mounted on the housingpart (2,4); an eccentric pin (14) on the rotatable knob (8); and whereinwhen the rotatable knob (8) is rotated the eccentric pin (14) is rotatedand slideably engages with the mode change member (68) in order to shiftthe mode change member (68) to shift the mode change sleeve (52) amongstits three positions.
 12. The rotary hammer according to claim 1, whichfurther comprises: a biasing arrangement (76,78) which is locatedbetween the actuator 8 and the mode change sleeve (52) in order to biasthe mode change sleeve (52) towards the position on the intermediateshaft (24) which corresponds to the position to which the actuator (8)is switched.
 13. The rotary hammer according to claim 1, which furthercomprises: a mode change member (68); a mode change arm (72) on the modechange member (68); a biasing arrangement (76,78), which comprises: afirst spring member (76); and a second spring member (78); wherein themode change arm (72) extends laterally of the mode change member (68)and at least partly surrounds a part of the mode change sleeve (52) andis connected to the mode change sleeve (52) such that shifting of themode change member (68) shifts the mode change sleeve (52) through themode change arm (72) amongst its three positions; the biasingarrangement (76,78) located between the actuator (8) and the mode changesleeve (52) in order to bias the mode change sleeve (52) towards theposition on the intermediate shaft (24) which corresponds to theposition to which the actuator (8) is switched; and the first springmember (76) located between a forward end of the mode change sleeve (52)and a forward facing part of the mode change arm (72) and the secondspring member (78) located between a rearward end of the mode changesleeve (52) and a rearward facing part of the mode change arm (72). 14.The rotary hammer according to claim 1, which further comprises; aspindle lock (70) to lock the spindle (18) against rotation when therotary hammer is in a hammer only mode.
 15. The rotary hammer accordingto claim 14, which further comprises: a mode change member (68); thespindle lock (70) comprising: a first locking member (70); and a secondlocking member (62,64); and wherein the switching of the single actuator(8) shifts the mode change sleeve (52) through the mode change member(68) and the first locking member (70) is located on the mode changemember (68) and engages the second locking member (62,64) located on thespindle (18) when the mode change member (68) is shifted to a hammeronly mode position to lock the spindle (18) against rotation.
 16. Therotary hammer according to claim 1, which further comprises: thepneumatic hammering arrangement comprising: a ram (21); a reciprocallydriven piston (20) which is reciprocally drives the ram (21) through aclosed air cushion; and an anvil (22) which is repeatedly impacted bythe ram (21) and, in turn, impacts the bit or tool held in the toolholder (16).
 17. The rotary hammer according to claim 1, wherein theintermediate shaft (24) is substantially parallel to the spindle (18).18. The rotary hammer according to claim 1, wherein: the spindle drivemember (56) comprises: a driving member (60); a driven member (62),which forms a part of the spindle drive arrangement (62,64); and whereinthe driving member (60) is in permanent engagement with the drive member(62).
 19. The rotary hammer according to claim 1, wherein the hammerdrive arrangement is a wobble plate arrangement (36,38,39,40).
 20. Therotary hammer according to claim 1, which further comprises: areleasable detent arrangement (90,92,94) for releasably latching theactuator (8) in a mode switch position.
 21. The rotary hammer accordingto claim 1, wherein the mode change sleeve is a single sleeve.
 22. Arotary hammer comprising: a housing; a tool holder coupled to thehousing and configured to releasably hold a tool; a spindle configuredto rotate about a first longitudinal axis of the spindle to causedrilling motion of a tool held within the tool holder; a piston thatreciprocates within the spindle along the first longitudinal axis tocause hammering motion of a tool held within the tool holder; a motor atleast partially disposed in the housing; an intermediate shaftconfigured to be rotated about a second longitudinal axis by the motorwhen power is supplied to the motor; a spindle drive mechanism coupledto at least one of the intermediate shaft and the spindle to selectivelytransmit rotary motion of the intermediate shaft to rotary motion of thespindle; a piston drive mechanism coupled to at least one of theintermediate shaft and the piston to selectively transmit rotary motionof the intermediate shaft to reciprocal motion of the piston; a modechange mechanism configured to select among a drilling mode, a hammeringand drilling mode, and a hammering mode, the mode change mechanismincluding a front sleeve portion and a rear sleeve portion eachshiftable along the intermediate shaft and permanently driven by theintermediate shaft to change the operation of the rotary hammer tooperate in any of the three modes, wherein the front sleeve portion ismoveable along the second longitudinal axis to selectively couple thespindle drive mechanism to the intermediate shaft when in the drillingmode and the hammering and drilling mode to transmit rotary movement ofthe intermediate shaft to rotary movement of the spindle and toselectively decouple the spindle drive mechanism from the intermediateshaft when in the hammering mode so that rotation of the intermediateshaft does not cause rotation of the spindle, and wherein the rearsleeve portion is moveable along the second longitudinal axis toselectively couple the piston drive mechanism to the intermediate shaftwhen in the hammering and drilling mode and the hammering mode totransmit rotary movement of the intermediate shaft to reciprocatingmovement of the piston and to selectively decouple the piston drivemechanism from the intermediate shaft when in the drilling mode so thatrotation of the intermediate shaft does not cause reciprocating movementof the piston; an actuator switch moveable among three positionscorresponding to the drilling mode, the hammering and drilling mode, andthe hammering mode; and a linkage that links the actuator switch to themode change mechanism to effectuate the movement of the front and rearsleeve portions upon movement of the actuator switch.
 23. The rotaryhammer according to claim 22, wherein the front sleeve portion comprisesa projection that can be selectively engaged with a recess on thespindle driving member when the mode change mechanism is in the drillingmode and the drilling and hammering mode.
 24. The rotary hammeraccording to claim 22, wherein the rear sleeve portion comprises aprojection that can be selectively engaged with a recess on the hammerdriving member when the mode change mechanism is in the hammering modeand the drilling and hammering mode.
 25. The rotary hammer according toclaim 24, wherein the front sleeve portion comprises a projection thatcan be selectively engaged with a recess on the spindle driving memberwhen the mode change mechanism is in the drilling mode and the drillingand hammering mode.
 26. The rotary hammer according to claim 22, whereinthe linkage comprises a bar that extends substantially parallel to thesecond longitudinal axis and at least one arm that extends laterallyfrom the bar, the at least one arm being coupled to the mode changemechanism such that shifting of the bar along the second longitudinalaxis moves the mode change mechanism among the drilling mode, thedrilling and hammering mode, and the hammering mode.
 27. The rotaryhammer according to claim 22, wherein the actuator switch comprises arotatable knob mounted on the housing and an eccentric pin coupled tothe rotatable knob, wherein when the rotatable knob is rotated theeccentric pin is rotated and slideably engages with the linkage in orderto shift the mode change mechanism among the drilling mode, the drillingand hammering mode, and the hammering mode.
 28. The rotary hammeraccording to claim 22, further comprising a spring that biases the modechange mechanism toward one of the drilling mode, the drilling andhammering mode, and the hammer mode.
 29. The rotary hammer according toclaim 28, wherein the spring biases the front sleeve portion of the modechange mechanism to couple the intermediate shaft to the spindle drivemechanism.
 30. The rotary hammer according to claim 28, wherein thespring biases the rear sleeve portion of the mode change mechanism tocouple the intermediate shaft to the piston drive mechanism.
 31. Therotary hammer according to claim 22, further comprising a spindle lockmember to lock the spindle against rotation when the rotary hammer is inthe hammering mode.
 32. The rotary hammer according to claim 31, whereinthe spindle lock member comprises a set of teeth that are fixed againstrotation and that are moveable substantially parallel to the secondlongitudinal axis with the linkage to bring the set of teeth intoengagement with the spindle drive mechanism.
 33. The rotary hammeraccording to claim 22, further comprising a ram that is reciprocallydriven by the piston through an air cushion, and an anvil that isrepeatedly impacted by the ram and that, in turn, impacts the tool heldin the tool holder.
 34. The rotary hammer according to claim 22, whereinthe intermediate shaft is substantially parallel to the spindle.
 35. Therotary hammer according to claim 22, wherein the spindle drive mechanismcomprises a first splined ring gear that is permanently fixed to thespindle and a second splined ring gear that engages the first splinedring gear, wherein the front sleeve portion of the mode change mechanismcauses the second splined ring gear to rotate with the intermediateshaft.
 36. The rotary hammer according to claim 22, wherein the pistondrive mechanism comprises a wobble drive mechanism that converts rotarymotion of the intermediate shaft to reciprocal motion of the piston. 37.The rotary hammer according to claim 22, wherein the actuator includes areleasable detent arrangement that releasably latches the actuator in atleast one of the three positions.
 38. The rotary hammer according toclaim 22, wherein front sleeve portion and the rear sleeve portion aredisposed on a single mode change sleeve.